A variety of types of strip feeding devices are used for feeding strip material along a feed path such as sprocket feeds, roll feeds and feeding mechanisms having reciprocating clamps of the type commonly referred to as hitch feeds. Sprocket feeds require that spaced apart holes be punched in the strip adjacent to the side edges thereof for reception of sprocket teeth. Roll feed mechanisms are suitable where flat strip is being fed and are particularly useful where feeding takes place continuously. Reciprocating feeding mechanisms, such as hitch feeds as used on metal stamping and forming presses, comprise a reciprocating clamp which advances the strip during each stroke of the clamp.
The feeding mechanisms discussed above all require that when intermittent feeding is being carried out, the feeding mechanism itself must be stopped during non-feeding or dwell intervals and set in motion at the beginning of every feeding interval for the strip. For example, a common hitch feed of the type used on stamping and forming machine comprises reciprocating clamp which is closed onto the strip during the feed stroke, which is opened to unclamp the strip at the end of the feed stroke, and which is then returned to its starting position prior to the succeeding feed stroke. The inertia of the parts of the feeding mechanism must thus be overcome when the feeding mechanism is stopped and the mechanism must be set in motion when the feeding mechanism is started. This feature results in relatively high power requirements for the feed mechanism, far greater than are required for moving the strip and limits the frequency with which strip can be fed intermittently during a given time interval. For example, a punch press operating at a speed of 500 strokes per minute requires that the reciprocating clamp of the feeding mechanism be reciprocated at the same speed.
The present invention is directed to a feeding means for strip material which can be used under a wide variety of circumstances and which overcomes many of the shortcomings of known types of strip feed mechanisms as described above. The invention is further directed to the achievement of a strip feeding apparatus having feeding parts which continuously rotate at a constant speed and which is capable of feeding the strip intermittently, at a constant speed, or at cyclically changing speeds during each feeding cycle. One embodiment of the invention is directed to a feeding apparatus which can be used with metal stamping and forming machines and which will substantially reduce the power requirements for feeding the strip and will permit higher cycle rates of the machine than were heretofore practical.
A preferred embodiment of the invention comprises a strip feeding apparatus for feeding strip along a strip feed path. The strip has at least one straight edge and has notches in the straight edge. The strip feeding apparatus is of the type comprising a strip feeder, an edge guide, and a side guide, the edge guide and the side guide extending at least partially along the feed path and serving to guide the strip along the feed path while the strip is being fed by the feeder. The apparatus is characterized in that the strip feeder comprises a thread support and a feeding thread on the surface of the thread support. The thread support is mounted for rotation on an axis of rotation which extends substantially parallel to the strip feed path and adjacent to the straight edge of a strip on the feed path. The thread is dimensioned to be received in the notches in the strip. A strip retainer is provided for maintaining the straight edge of the strip adjacent to the thread support with the thread extending into at least one notch in the strip. An actuating means is provided for rotating the thread support so that during rotation of the thread support, the thread moves the strip along the strip feed path.
In accordance with a further embodiment, the thread extends for a plurality of turns around the thread support, and each turn of the thread has a strip feeding portion and a strip dwell portion. The strip feeding portion extends substantially helically with respect to the axis of rotation and the strip dwell portion extends along a circular path, the plane defined by the circular path being normal to the plane of the strip. During continuous rotation of the thread support the strip is fed intermittently along the feed path during feeding intervals and the strip dwells during dwell intervals which are between feeding intervals.
In accordance with a further embodiment, the strip feeder comprises at least one pair of thread supports and at least one pair of feeding threads. The pair of thread supports are spaced apart along the axis of rotation and an operating station is provided on the strip feed path between the pair of thread supports for performing an operation on the strip. The operating station may comprise a pair of opposed tool holders which are reciprocable relatively towards and away from each other between open positions, in which the tool holders are remote from each other, and closed positions, in which the tool holders are adjacent to each other, the tool holders having tools thereon for performing an operation on the strip. The thread supports and the tool holders may be adjustable relative to each so that the strip can be precisely positioned in the operating station with respect to the tool holders during dwell intervals.
In accordance with a further embodiment, a strip notching punch and die are provided at a location upstream, relative to the direction of strip feed, from the strip feeder. Punch and die actuating means are provided to move the punch relatively through the die during dwell of the strip thereby to form the notches in the strip. The punch may be provided on a punch support which is mounted for rotation on the axis of rotation of the thread support.
In accordance with a further embodiment, the strip feeder comprises a thread support and a strip guide arranged such that the feeding thread on the thread support engages one edge of strip material in the guide and advances the material during rotation of the thread support.